The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
As fast as the multimedia-related technology advances at unprecedented pace, demands for high quality of multimedia data such as audio, images, and videos are increasing. As a part of the development, international standards have been established on high efficiency video compressions to satisfy the needs for transmission, storage, and retrieval of such multimedia data within limited network resources. Especially for an international standard on video compressions, ISO/IEC JTC1/SC29 MPEG group and ITU-T VCEG group have created H.264/AVC MPEG-4 Part.10 standard, which attempts to achieve a high compression efficiency by using various prediction encoding methods such as variable block size motion estimation and compensation, intra prediction encoding, etc.
Through the motion estimation, motion vectors are generated and used to compensate the motions, and the conventional method of encoding/decoding the motion vectors in the video encoding/decoding space is to perform a prediction encoding with respect to a motion vector of a block estimated by using motion vectors of spatially adjacent blocks as predicted values. That is, because the motion vector of the current block has high correlations with motion vectors of the adjacent blocks, these motion vectors are used in calculating the predicted values which are generated as predicted motion vectors (PMV), and then an encoding is performed not on the true value of the motion vector of the current block but just on its differential values from PMVs in an effort to reduce the bit rate required to encode the motion vectors and improve the encoding efficiency.
Therefore, according to the typical motion vector encoding methods, the efficiency of compression is increased as the predicted motion vectors get closer to a motion vector of the current block. However, to have the closest predicted motion vectors relative to the motion vector of the current block, it is necessary to additionally encode information on what values to use as the predicted motion vectors which adds to the bit rate and deteriorates in the compression efficiency.